1. Field of the Disclosure
The present disclosure relates to an organic light-emitting diode, and more particularly, to an organic light-emitting diode capable of reducing the number of masks required in a fabrication process to thereby reduce a fabricating cost and simplify the fabrication process, and a method of fabricating the organic light-emitting diode.
2. Discussion of the Related Art
A cathode ray tube (CRT) has been used as a display for various electronics for a long time. However, recently, flat panel display devices, such as a plasma display panel (PDP), a liquid crystal display (LCD), and an organic light-emitting diode (OLED) display device, have been developed and widely used.
Among the above-mentioned flat panel display devices, the organic light-emitting diode display device can be fabricated as a lightweight, slim display since it is a self-luminous device requiring no backlight.
Also, the organic light-emitting diode display device has low consumption power, allows direct-current low-voltage driving, has a high response speed, is highly resistant to external impacts since the internal element is solid, and also has a wide operating temperature range.
Particularly, since the organic light-emitting diode display device can be fabricated with a simple fabrication process, it can be fabricated with a lower fabrication cost than a liquid crystal display device.
FIG. 1 is a circuit diagram showing the structure of a pixel of a conventional active matrix type organic light-emitting diode display device.
Referring to FIG. 1, a pixel of the active matrix type organic light-emitting diode display device includes a switching thin film transistor STr, a driving thin film transistor DTr, a storage capacitor StgC, and an organic light-emitting diode E.
Also, gate lines GL are formed in a first direction, data lines DL are formed in a second direction crossing the first direction, and a power line PL for supplying a voltage is formed to be spaced apart from a data line DL.
The switching thin film transistor STr is formed at a crossing of a data line DL and a gate line GL, and electrically connected to the driving thin film transistor DTr.
The driving thin film transistor DTr is electrically connected to the organic light-emitting diode E. That is, a first electrode of the organic light-emitting diode E corresponding to one terminal of the organic light-emitting diode E is connected to the drain electrode of the drain thin film transistor DTr, and a second electrode of the organic light-emitting diode E corresponding to the other terminal of the organic light-emitting diode E is connected to the ground. The power line PL transfers a supply voltage to the organic light-emitting diode E. Also, the storage capacitor StgC is formed between the gate electrode and source electrode of the driving thin film transistor DTr.
Accordingly, if a signal is applied through the gate line GL, the switching thin film transistor STr is turned on, a signal of the data line DL is transferred to the gate electrode of the driving thin film transistor DTr to turn on the driving thin film transistor DTr, so that light is emitted through the organic light-emitting diode E. If the driving thin film transistor DTr is turned on, a level of current flowing from the power line PL to the organic light-emitting diode E is decided so that the organic light-emitting diode E can implement a gray scale. Also, the storage capacitor StgC acts to maintain the gate voltage of the driving thin film transistor DTr constant when the switching thin film transistor STr is turned off, to thereby maintain the level of the current flowing through the organic thin film diode E constant until a next frame even when the switching thin film transistor STr is turned off.
As shown in FIG. 2, the organic light emitting diode E includes an anode 10 on which red, green, and blue pixel areas Rp, Gp, and Bp are defined, a hole transporting layer 12, an emitting material layer consisting of a red organic light-emitting pattern 14, a green organic light-emitting pattern 16, and a blue organic light-emitting pattern 18, an electron transporting layer 20, and a cathode 22. Although not shown in FIG. 2, a hole injection layer may be disposed between the anode 10 and the hole transporting layer 12, and an electron injection layer may be disposed between the cathode 22 and the electron transporting layer 20
In the organic light-emitting diode E, if voltages are applied to the anode 10 and the cathode 22, holes and electrons are transferred to the emitting material layer, and coupled with each other in the emitting material layer to thereby emit light. However, the conventional organic light-emitting diode has limitations in light output efficiency and color properties.